Need schematic for Pro-2055

[moondog52]

Probably asked somewhere evry day If anyone can point me to any schematic info for the 2055 I'd sure appreciate it. Have a unit where the front panel is *all* dead ... not even keypad leds ... sure seems like it must be a bad diode or voltage supply problem, but the 8v and 3.5v sources both seem to be getting to chips and display there.

Thanks in advance.

N7XSS at arrl.net

 

[buttons]

There were a bunch of bad 2055s out there. Saeial 09Ao5 & 6 were 2 of them All lost the display. I'm on my fourth c031339 now. 6mos and praying.

 

[moondog52]

Thank you, but I'm quite aware of that. In those cases the backlighting on the LCD display still works and the same for the LEDs on the front panel. This situation is different, and unfortunately more complicated.

You haven't got a schematic in yer back pocket by chance?

 

[pro92b]

A few questions:

Do the squelch and volume control work - do you get white noise when the controls are adjusted?

Does the key beep work when you press a key?

If you press WX does the radio pick up a weather station?

The LED's and display are both controlled by the microprocessor. If it or a supporting component (clock crystal, EEPROM) is bad the radio will be esentially brain dead.

Check the ribbon cable that connects the main board to the logic board for bad solder joints at the logic board. Disconnect the cable at the main board by pulling up on the latch on the zero insertion force socket and extracting the cable. Inspect the contacts and reseat the cable.

Try resetting the scanner as detailed on P. 85 of the owner's manual. If no improvement then do the initialization procedure.

 

[moondog52]

Thanks for the reply pro ...

Yeah, volume works but not the squelch. White noise yes (not sure where the discriminator chip is located yet). WX no. Been thru all the main ribbon cable and confirmed connectivity to the display board side. LM317 is putting 3.5 VDC up to the main processor and the display. Spent a lot of time touching up connections ... and looking for shorts. I did try the reset of course.

The 7808 is getting to the display board (via the ribbon cable) but not sure what it's used for ... I'm guessing it might supply voltage for the keypad LEDs and the backlight of the LCD.

So I think there's someting in that 8v path that is where the problem is ... seems to me like I should be able to at least get a lit LCD backlight and keypad LEDs. I find it hard to believe that those would be dependent on the CPU firing up ... but who knows? I just pulled out my component tester & 'scope so I'll give the diodes a scan tomorrow.

This was a $60 "special" ... all new in the box, so I knew I was rolling the dice ... but I'm a gambler and a chess player Sure wish they would make it a law to supply schematics these daze ...

tnx agn DE N7XSS

 

[pro92b]

LED's do depend on the CPU for operation. The DIM button on the keypad sends commands to the CPU which then sets LED brightness.

Squelch muting also is controlled by the CPU. Considering all the unrelated functions that are not working, the common thread is the CPU.

You might probe in the area of the clock crystal to check that the clock is working. If it is then the CPU itself may be bad.

 

[moondog52]

Oscillator (CPU X1, X2 pins) doesn't seem to be running. I'll check it out a bit more, but it looks like I've just about taken it as far as I can ... oh well, can't win them all

Thanks for that last post ... I needed to know that info.